5/11/2013 Computer Graphics CSC3406 1 Bài 13 Render This Week  We will examine: – Visual Realism  Lighting  Shading  Texturing; and  Shadowing 5/11/2013 Computer Graphics CSC3406 2 Visual Realism  When rendering (painting) an image we need to consider the factors that will make the scene appear real.  Provides a “suspension of disbelief” for the viewer. e.g. Shrek 5/11/2013 Computer Graphics CSC3406 3 Visual Realism  Lowest Level is Wireframe – Outline of Solids – Quick to render – OpenGL takes care of hidden lines. 5/11/2013 Computer Graphics CSC3406 4 Visual Realism  Flat Shading – Each polygon is shaded in the same tone. – Amount of light is calculated from a single point on the surface. – Same normal applies for whole surface. 5/11/2013 Computer Graphics CSC3406 5 Visual Realism  Smooth Shading – Gouraud Shading – Different grey levels are used across a polygon by interpolating the difference between vertices. 5/11/2013 Computer Graphics CSC3406 6 Shading Models  Shading Model – how light is scattered or reflected from a surface – frequently presupposes that two types of light sources illuminate the objects in a scene: point light and ambient light – light can be absorbed, reflected and refracted. 5/11/2013 Computer Graphics CSC3406 7 Shading Models  Reflection – diffuse scattering: some light penetrates the surface and is re- radiated uniformly in all directions – specular reflection: mirrorlike and highly directional 5/11/2013 Computer Graphics CSC3406 8 Reflected Light  m is a vector normal to the surface at P  s is the vector from P to the light  v is the vector from P to the viewer 5/11/2013 Computer Graphics CSC3406 9 Reflected Light  The amount of reflected light can be calculated using the angles between these vectors.  A mesh has two sides. We need to calculate the light for the side we are viewing from.  This is why it is important that we have the right normal vector. 5/11/2013 Computer Graphics CSC3406 10 . Bài 13 Render This Week  We will examine: – Visual Realism  Lighting  Shading  Texturing; and  Shadowing 5/11/2013 Computer Graphics CSC3406 2 Visual Realism  When rendering. Graphics CSC3406 3 Visual Realism  Lowest Level is Wireframe – Outline of Solids – Quick to render – OpenGL takes care of hidden lines. 5/11/2013 Computer Graphics CSC3406 4 Visual Realism